Primary astrocyte cultures have been shown to have adrenergic Alpha and Beta receptors. Activation of Beta receptors leads to large increases in intracellular cyclic AMP levels which are potentiated by inhibition of the Alpha receptor indicating some degree of receptor "cross-talk". In addition, we have found that these cells have both high and low affinity uptake sites for catecholamines which are associated with metabolism, and that high affinity uptake is inhibited by nanomolar concentrations of tricyclic antidepressants. Since there appears to be both receptors and uptake sites for at least norepinephrine on the same cells, it will be of great interest to examine how receptor activity affects uptake of its agonist by studying the effects of receptor antagonists on uptake, or coversely, the effects of inhibitors of uptake in receptor activity. We also propose to further examine the kinetics of monoamine uptake and determine sensitivity to inhibitors, particularly antidepressant drugs. We will compare the pharmacology of a norepinephrine-induced depolarization we have recently observed with the pharmacology of the cAMP response. We will look for any potentiation of the depolarization response by antidepressants due to effects on uptake, and also direct effects of such drugs. We will also examine uptake of catecholamines by fluorescence microscopy. The techniques used will include use of radiolabelled agonists or antagonists to quantitatively measure uptake and binding by the cells. Radioimmune assays will be used for measuring cAMP levels, and enzyme acitivity of adenyl cyclase will also be assayed. Standard microelectrode techniques will be used for electrophysiology. We will use the glycoxylic acid method for examining uptake of catecholamines by fluorescence. The concept that astrocytes have both receptors and uptake sites for catecholamines has only recently been indicated by work using cell cultures as experimental models for astrocytes. Our proposed experiments should provide a clearer picture of the mechanisms and the interactions of these two processes, and also see if 5 hydroxytryptamine is involved. Astrocytes are a major cell constituent of the mammalian CNS. Thus, these findings are significant in indicating a possible and hitherto unexpected role for astrocytes in the electrophysiological and biochemical effects of monomine action in the mammalian CNS, and thus may be involved in the mechanisms of mental illness, especially affective disorders.